The Kowari: Saving a Central Australian Micro-Predator
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Magazine of the Threatened Species Recovery Hub The kowari: Saving a central Australian micro-predator IMAGE: NATHAN BEERKENS The roles that medium- and micro-predators play in ecosystems were first noted ABOVE: A kowari on a gibber plain in the by Darwin. He observed that field mice prey upon “humble” bee nests, and that Sturts Stony Desert in South Australia, one of the last strongholds of the tiny predator. the abundance of cats in a district, through suppression of mice, may increase the flowering success of certain plants, such as clover. Here, Aaron Greenville, Katherine Tuft, Rob Brandle and Chris Dickman discuss how the Australian arid zone is an ideal place to examine Darwin’s observation and its implications as they undertake research to help secure the future of the kowari. The rise of micro-predators The biology of the kowari Adult kowaris weigh up to 175 g (males) Micro-predators are defined as weighing less The kowari is a small nocturnal dasyurid or 140 g (females), which highlights the than 300 g. They are present on most of the predator whose diet consists of invertebrates vulnerability of the species: it lies within the Earth’s land surface and play an important and rodents. During the day, this species critical weight range (35–5500 g) of mammals role, through their predation, in food webs. shelters in burrows that it digs into sand most prone to extinction in Australia. Interactions within groups of micro-predators mounds. Such mounds occur infrequently Kowari populations have declined across the can be subtle, yet pervasive. One example, across stony gibber environments in arid central Australian deserts, and the species from cool temperate forests in Asia, is a Australia, where temperatures often exceed currently has only a very limited distribution. decrease in spider numbers in the presence 40°C in summer and fall below 5°C in winter. The few populations that remain are located of the long-clawed shrew (Sorex unguiculatus), which leads to an increase in the spider’s prey, BELOW LEFT: Checking a pregnant kowari pouch. BELOW RIGHT: William La Marca inspecting a kowari. tiny springtails. An example from closer to home is that of the insectivorous marsupials (dasyurids). The presence of the larger brush-tailed mulgara (Dasycercus blythi) increases the diversity and number of these smaller desert dasyurid marsupials, such as the wongai ningaui (Ningaui ridei), through the suppression of dunnart species (Sminthopsis spp.). The loss of top predators from regions around the world is leaving micro-predators as the dominant predators in many ecosystems. The need to understand and conserve these species and their ecological functions is therefore more vital than ever. 6 Science for saving species #11 IMAGE:TALI MOYLE IMAGE: TALI MOYLE in arid South Australia and western Queensland. In these central desert regions, drought–wet cycles are driven principally by the El Niño Southern Oscillation, and are particularly intense. With the decline or extinction of larger native arid zone predators, such as the western quoll, the possibility exists of the kowari now rising as an influential micro- predator in these desert regions. It is a similar size to the brush-tailed mulgara discussed above, and has the potential to hold a similarly important role in structuring and promoting biodiversity in arid Australia. Securing the kowari’s populations could then be critically IMAGE: AARON GREENVILLE important not just for its own sake, but also to maintain diversity in these regions. What we are doing now ABOVE: Brush-tailed mulgara in the Simpson Desert. Extinction risk for the kowari Given these alarming results, we are recommending that the kowari be considered For further information Recent research by our team drawn from for listing as Endangered. Working with Aaron Greenville and Chris Dickman, The University of Sydney and the South stakeholders, such as pastoralists, the The University of Sydney, New South Wales Australian Government found that the kowari Traditional Owners of land now managed populations in South Australia declined – [email protected] as national parks through co-management over the period 2000–2015. This finding – [email protected] boards, and Arid Recovery (on a property was in spite of relatively favourable climate that has excluded introduced predators and Katherine Tuft, Arid Recovery, South Australia conditions over the period and some evidence is dedicated to research), we hope to return – [email protected] that both the body condition of kowaris and the kowari to its former strongholds and a their rate of reproduction increased after Rob Brandle, Department for Environment predator-free reserve to learn about how rain. Further, the region where we surveyed and Water, South Australia to manage its conservation effectively. kowaris featured favourable habitat. This leads – [email protected] us to suggest that the two studied populations A PhD project by William La Marca is also are under stress from pressures that are investigating the major threats to the READ MORE HERE external rather than threats arising from survival of the kowari – currently thought to within the species itself. be predation by feral cats, a medium-sized predator, and habitat disturbance due to cattle The two populations of kowaris showed grazing – and how to mitigate them. The roles “Hence it is quite credible that the highly similar trajectories. This is not good that Darwin first noted medium- and micro- news, because when two adjacent populations presence of a feline animal in large predators to play in the ecosystem, and their are both declining it reduces the opportunity numbers in a district might determine, implications for biodiversity, are thus being for them to recolonise each other, and points enacted – and investigated – on the stony through the intervention first of mice to an increased risk of extinction. In fact, the gibber plains of South Australia. and then of [bumble] bees, the frequency results from the population viability analysis suggest that, if similar trends occur elsewhere This Threatened Species Recovery Hub project of certain flowers in the district.” is a collaboration between The University in other populations, the species would be of Sydney, Arid Recovery, the South Australian Darwin, C. (1859), On the Origin of eligible for listing on the IUCN Red List as Department for Environment and Water Species by Means of Natural Selection. Endangered, due to a 20% chance of and the Foundation for Australia’s Most London: John Murray, p. 74. extinction within the next 20 years. Endangered Species (FAME). We thank Jim Phillipson for his recent support of this project. BELOW: Many regions are suffering declines in top predators like dingoes, leaving micro-predators as the dominant predator in the ecosystem. IMAGE: WILLIAM LA MARCA 7.